Surprised that there hasn't been more discussion on him considering how highly regarded he is.

Quoting large sections of wikipedia:

Bogart was proud of his success, but the fact that it came from playing a gangster weighed on him. He once said: "I can't get in a mild discussion without turning it into an argument. There must be something in my tone of voice, or this arrogant face—something that antagonizes everybody. Nobody likes me on sight. I suppose that's why I'm cast as the heavy." Bogart's roles were not only repetitive, but physically demanding and draining (studios were not yet air-conditioned), and his regimented, tightly scheduled job at Warners was not exactly the "peachy" actor's life he hoped for. However, he was always professional and generally respected by other actors. In those "B movie" years, Bogart started developing his lasting film persona—the wounded, stoical, cynical, charming, vulnerable, self-mocking loner with a code of honor.

Amenities at Warners were few compared to those for their fellow actors at MGM. Bogart thought that the Warners wardrobe department was cheap, and often wore his own suits in his movies.

On August 21, 1938, Bogart entered into a disastrous third marriage, with actress Mayo Methot, a lively, friendly woman when sober, but paranoid when drunk. She was convinced that her husband was cheating on her. The more she and Bogart drifted apart, the more she drank, got furious and threw things at him: plants, crockery, anything close at hand. She even set the house on fire, stabbed him with a knife, and slashed her wrists on several occasions. Bogart for his part needled her mercilessly and seemed to enjoy confrontation. Sometimes he turned violent. The press accurately dubbed them "the Battling Bogarts." "The Bogart-Methot marriage was the sequel to the Civil War," said their friend Julius Epstein. A wag observed that there was "madness in his Methot." During this time, Bogart bought a motor launch, which he named Sluggy, after his nickname for his hot-tempered wife. Despite his proclamations that, "I like a jealous wife," "We get on so well together (because) we don't have illusions about each other," and, "I wouldn't give you two cents for a dame without a temper," it was a highly destructive relationship.

In California in 1945, Bogart bought a 55-foot (17 m) sailing yacht, the Santana, from actor Dick Powell. The sea was his sanctuary and he loved to sail around Catalina Island. He was a serious sailor, respected by other sailors who had seen too many Hollywood actors and their boats. About 30 weekends a year, he went out on his boat. He once said, "An actor needs something to stabilize his personality, something to nail down what he really is, not what he is currently pretending to be."

Bogart had a lifelong disgust for the pretentious, fake or phony, as his son Stephen told Turner Classic Movies host Robert Osborne in 1999. Sensitive yet caustic, and disgusted by the inferior movies he was performing in, Bogart cultivated the persona of a soured idealist, a man exiled from better things in New York, living by his wits, drinking too much, cursed to live out his life among second-rate people and projects.

Bogart rarely saw his own films and avoided premieres. He even protected his privacy with invented press releases about his private life to satisfy the curiosity of the newspapers and the public. When he thought an actor, director, or a movie studio had done something shoddy, he spoke up about it and was willing to be quoted. He advised Robert Mitchum that the only way to stay alive in Hollywood was to be an "againster." As a result, he was not the most popular of actors, and some in the Hollywood community shunned him privately to avoid trouble with the studios. But the Hollywood press, unaccustomed to candor, was delighted. Bogart once said:

All over Hollywood, they are continually advising me, "Oh, you mustn't say that. That will get you in a lot of trouble," when I remark that some picture or writer or director or producer is no good. I don't get it. If he isn't any good, why can't you say so? If more people would mention it, pretty soon it might start having some effect.

The producer Arthur Hopkins heard the play from off-stage and sent for Bogart to play escaped murderer Duke Mantee in Robert E. Sherwood's new play, The Petrified Forest. Hopkins recalled:

When I saw the actor I was somewhat taken aback, for he was the one I never much admired. He was an antiquated juvenile who spent most of his stage life in white pants swinging a tennis racquet. He seemed as far from a cold-blooded killer as one could get, but the voice (dry and tired) persisted, and the voice was Mantee's.

Bogart met Lauren Bacall while filming To Have and Have Not (1944), a loose adaptation of the Ernest Hemingway novel. The movie has many similarities with Casablanca—the same enemies, the same kind of hero, even a piano player sidekick (this time Hoagy Carmichael). When they met, Bacall was 19 and Bogart was 44. He nicknamed her "Baby." She had been a model since she was 16 and had acted in two failed plays. Bogart was drawn to Bacall's high cheekbones, green eyes, tawny blond hair, and lean body, as well as her poise and earthy, outspoken honesty. Reportedly he said, "I just saw your test. We'll have a lot of fun together". Their physical and emotional rapport was very strong from the start, and the age difference and different acting experience also created the additional dimension of a mentor-student relationship. Quite contrary to the Hollywood norm, it was his first affair with a leading lady. Bogart was still miserably married and his early meetings with Bacall were discreet and brief, their separations bridged by ardent love letters. The relationship made it much easier for the newcomer to make her first film, and Bogart did his best to put her at ease by joking with her and quietly coaching her. He let her steal scenes and even encouraged it. Howard Hawks, for his part, also did his best to boost her performance and her role, and found Bogart easy to direct.

Hawks said of Bacall: "Bogie fell in love with the character she played, so she had to keep playing it the rest of her life."

Bogart and Bacall moved into a $160,000 (equal to $2,095,970 today) white brick mansion in an exclusive neighborhood in Holmby Hills. The marriage proved to be a happy one, though there were the normal tensions due to their differences. He was a homebody and she liked nightlife; he loved the sea, which made her seasick. Bogart's drinking sometimes inflamed tensions.

LII
His first wife beat the crap out of him and he stayed in that relationship for ever.

It's possible he's LSI, but he was way too much of a pushover to be one.

he could be an LSI and hmm, i think his stoicism was mistaken for pushover-ness. LSIs can shut you off completely if you yell at them by putting you on ignore mode.
and well, lol, sadism - appeal of the beta relationships haha